<template>
    <div class="xtx-carousel" @mouseenter="stop()" @mouseleave="start()">
        <ul class="carousel-body">
            <li class="carousel-item" v-for="(item, i) in sliders" :key="i" :class="{fade:index === i}">
                <RouterLink to="/">
                    <img :src="item.imgUrl" alt="加载中。。。">
                </RouterLink>
            </li>
        </ul>
        <a href="javascript:;" @click="toggle(-1)" class="carousel-btn prev"><i class="iconfont icon-angle-left"></i></a>
        <a href="javascript:;" @click="toggle(1)" class="carousel-btn next"><i class="iconfont icon-angle-right"></i></a>
        <div class="carousel-indicator">
            <span v-for="(item,i) in sliders" :key="i" :class="{active:index === i}"></span>
        </div>
    </div>
</template>

<script>
import { ref, watch, onUnmounted } from "vue";

export default {
    name: "XtxCarousel",
    props: {
        sliders: {
            type: Array,
            default: () => []
        },
        duration: {
            type: Number,
            default: 3000
        },
        autoPlay: {
            type: Boolean,
            default: false
        }
    },
    setup(props){
        // 默认显示的图片的索引
        const index = ref(0);

        // 自动播放
        let timer = null;
        const autoPlayFn = () => {
            clearInterval(timer);
            timer = setInterval(() => {
                index.value++;
                if (index.value >= props.sliders.length) {
                    index.value = 0;
                }
            }, props.duration);
        };

        watch(() => props.sliders, (newVal) => {
            // 有数据&开启自动播放，才调用自动播放函数
            if (newVal.length && props.autoPlay) {
                index.value = 0;
                autoPlayFn();
            }
        }, { immediate: true });

        // 鼠标进入停止，移出开启自动，前提条件：autoPlay为true
        const stop = () => {
            if (timer) clearInterval(timer);
        };
        const start = () => {
            if (props.sliders.length && props.autoPlay) {
                autoPlayFn();
            }
        };

        // 上一张下一张
        const toggle = (step) => {
            const newIndex = index.value + step;
            if (newIndex >= props.sliders.length) {
                index.value = 0;
                return;
            }
            if (newIndex < 0) {
                index.value = props.sliders.length - 1;
                return;
            }
            index.value = newIndex;
        };

        // 组件消耗，清理定时器
        onUnmounted(() => {
            clearInterval(timer);
        });

        return {
            index,
            stop,
            start,
            toggle
        };
    }
};
</script>
<style scoped lang="less">
.xtx-carousel {
    width: 100%;
    height: 100%;
    min-width: 300px;
    min-height: 150px;
    position: relative;

    .carousel {
        &-body {
            width: 100%;
            height: 100%;
        }

        &-item {
            width: 100%;
            height: 100%;
            position: absolute;
            left: 0;
            top: 0;
            opacity: 0;
            transition: opacity 0.5s linear;

            &.fade {
                opacity: 1;
                z-index: 1;
            }

            img {
                width: 100%;
                height: 100%;
            }
        }

        &-indicator {
            position: absolute;
            left: 0;
            bottom: 20px;
            z-index: 2;
            width: 100%;
            text-align: center;

            span {
                display: inline-block;
                width: 12px;
                height: 12px;
                background: rgba(0, 0, 0, 0.2);
                border-radius: 50%;
                cursor: pointer;

                ~ span {
                    margin-left: 12px;
                }

                &.active {
                    background: #fff;
                }
            }
        }

        &-btn {
            width: 44px;
            height: 44px;
            background: rgba(0, 0, 0, .2);
            color: #fff;
            border-radius: 50%;
            position: absolute;
            top: 228px;
            z-index: 2;
            text-align: center;
            line-height: 44px;
            opacity: 0;
            transition: all 0.5s;

            &.prev {
                left: 20px;
            }

            &.next {
                right: 20px;
            }
        }
    }

    &:hover {
        .carousel-btn {
            opacity: 1;
        }
    }
}
</style>
